On the 16th of December, 1671, he married Janet, only daughter and heiress of Alexander Brodie of Lethen, by whom he had five sons and four daughters. One of his daughters, Margaret, married the famous Simon Fraser, Lord Lovat, and had issue.

The Laird of Freuchie was elected one of the members of Parliament for the county of Elgin, and was present in the Parliament which was opened by the Duke of York at Edinburgh on the 28th of July, 1681. Grant ventured to vote against a clause in the Test Act. Four years later, in 1685, the laird and his wife were summoned to appear before the Commission appointed to prosecute all persons guilty of non-conformity and other crimes, between the bounds of the Spey and the Ness. They appeared before the Commissioners and were examined at length. They were both found guilty of having withdrawn from the Parish Church, and of hearing and countenancing unlicensed ministers. Therefore the Commissioners fined the laird for his own and his wife’s irregularities in the sum of £40,000 Scots, and ordered him to render payment to His Majesty’s cash keeper before the 1st of May next. A few days after the sentence was pronounced he was charged to make payment of the fine within 15 days, under the penalty of being put to the horn. Grant, however, resolved to make an effort to have the fine remitted. Reasons for the reconsideration and reversal of the sentence were framed and presented to the Privy Council, with a petition for review of the decree. Afterwards he sent a petition to James VII., who took a favourable view of the case, and, on the 9th of January, 1686, he addressed a letter to the Privy Council discharging the laird of the whole amount of the fine.

In the autumn of 1688 the Revolution was drawing nigh. In October the chief of the Grants was summoned to Edinburgh to receive the orders of the Privy Council; and on the 2nd of November he received a letter from the Duke of Gordon, governor of Edinburgh Castle, desiring him to raise a company of men for the service of King James. It seems probable that Grant did not respond to these letters.

On the 23rd of March he signed the address to King William. On the 26th he was elected a member of the Committee for settling the Government. This Committee consisted of eight peers, eight representatives of the counties, and eight representatives of the burghs; and they immediately proceeded to discuss and frame the decisive resolution. This resolution of the estates declared—" That James VII. had assumed the Royal power, and acted as king without ever taking the oath required by law; and by the advice of evil counsellors he had invaded the fundamental constitution of the kingdom, and altered it from a limited monarchy to an arbitary and despotic power; and did exercise the same to the subversion of the Protestant religion and the violation of the laws and liberties of the kingdom, whereby he forfeited his right to the crown, and the throne has become vacant"

He took an active part in raising men to assist General Mackay to overcome Viscount Dundee, and to restore peace and order in the Highlands. On the 24th of April, 1689, he was appointed, for the time, sheriff of Inverness-shire, and along with the other northern sheriffs, was commissioned to call a meeting of the heritors and fencible men within his jurisdiction, and to disperse any rebel forces.

He raised a regiment mainly consisting of the men of his own clan; but it appears that at first they were not well equipped. They were engaged at the Battle of Cromdale. The royal troops, under the command of General Livingstone, numbering about 1000 men, and 300 of the Grants were posted in Strathspey. The insurgents, under the command of General Buchan, and numbering about 800 men, marched through Badenoch and down Strathspey, and encamped on the Haughs of Cromdale. When tidings of Buchan’s advance reached Livingstone, he immediately resolved to march his force up the valley of the Spey, and on the 1st of May, 1690, at the break of day, attacked the enemy by surprise. The Highlanders were completely defeated, and a considerable number of them slain and taken prisoners, but, in the pursuit, the mist on the hills favoured their escape. This engagement brought the civil war, arising from the Revolution, to a close. The event was celebrated in a ballad which was long popular in the north, "The Haughs of Cromdale," beginning thus:-

As I came in by Auchindoun,
A little wee bit frae the town,
When to the Highlands I was bound,
To view the Haughs of Cromdale.

I met a man in tartan trews;
I speer’d at him what was the news;
Quo’ he "The Highland army rues
That ere we came to Cromdale.

"We were in bed, sir, every man,
When the English host upon us came,
A bloody battle then began
Upon the Haughs of Cromdale.

"The English horse they were so rude,
They bathed their hoofs in Highland blood,
But our brave clans, they boldly stood,
Upon the Haughs of Cromdale.

"But, alas! we could no longer stay,
For o’er the hills we came away,
And sore we do lament the day
That ere we came to Cromdale."

Before the date of the battle, the laird of Grant himself had returned to Edinburgh, and resumed his duties in Parliament. He took the oath of allegiance to the Government on the 15th of April, 1690. On the 14th of July, he was appointed one of the commissioners for visiting the universities and schools. In 1696 he signed the document which declared that William III. was truly and lawfully king, and bound the subscribers to defend His Majesty. In 1705 he joined in the protest against the union of the two kingdoms, unless the English Alien Bill was repealed.

On the 28th of February, 1694, he received from William III. a charter incorporating all the lands of Freuchie and other lands into a regality, to be called the Regality of Grant, and the castle and manor place of Freuchie to be henceforth called the Castle of Grant. At this time the Laird of Freuchie changed his designation to that of Laird of Grant—"Grant of Grant"

Castle Grant stands on an elevated site, one of the finest in Strathspey, and commands a wide and varied view of the surrounding country. The castle is a large structure, and was erected at different periods. A part of it was built by John Grant of Freuchie about 1525, and Sir Ludovick Grant, in the middle of the last century, made alterations and extensive additions to the castle. The dining hall is 47 feet in length and 27 in breadth. The park and the pleasure grounds are very extensive and varied.

The laird died at Edinburgh in November, 1716, and was interred in the Abbey Chapel of Holyrood. He was succeeded by his eldest surviving son, Colonel Alexander Grant of Grant. He was one of the Scottish Commissioners appointed to treat with England in 1706. He was a member of Parliament for Inverness-shire from 1703 till the last session of the Scottish Parliament in 1707. He usually voted with the Government.

He entered the army and attained the rank of brigadier-general. In 1708, at the first election in Scotland of members of the British Parliament, he was elected member for the county of Inverness. On the 24th of September, 1713, he was elected member of Parliament for the counties of Elgin and Nairn. He retired from the army in 1717.

In the spring of 1719 he was seized with a severe illness when in England. Although he recovered somewhat, and left London for Scotland in the beginning of August, and arrived at Leith on the 18th, the following day he died, and was interred in the Chapel of Holyrood.