Dear swamin
In case of a lady pregnant and her husband is missing who is next to continue
the function of sreemantham and when that is to be done. Also if her brother -in
-law is unmarried can he do the seemantham.

It is not srimantham, Seemantam.
Anybody can do but a gruhasthan.
To be done in 8th month.
Father in law is the preferable choice.
Next preference is elder brother in law - married.
or any elder couple.