The nominee for your Mutual fund holdings is the same as that of your Demat account. So, the nominee added to your Demat account will be the nominee for your Mutual Funds holdings as well.
Click here to know how to add a nominee to your Trading and Demat account.
Related articles:
how can i change or add a new nominee to my account
how to change or delete the nominee to my account
how to opt out of the nominee addition