The legal notice was sent by Gamde Gamlin after Richo allegedly made an "unfounded" public statement about rift between her sons Jarsa and Jarter Gamlin Ronya.
Demanding unconditional apology from Richo, Gamde accused him of defaming her and her family by giving false statement with an intent to show people that there is a tussle in the family for Liromoba seat which had fallen vacant after the death of Jarbom Gamlin on November 30 last year.
Jarsa Gamlin is a strong Congress contender for the bypoll scheduled on February 13.
However, when contacted over phone Richo, who is away in New Delhi, said that he has neither made any such statement nor got the legal notice.