HUF share for 1st marriage son

I got married in 2000, son born in 2001, marriage ended with divorce in 2004. Son stayed only with mother always (since we got separated during her pregnancy) and she got custody of son also. I gave huge amount of money to her & son as part of court divorce final settlement in 2004. I got remarried in 2008, have 2 children in 2nd marriage. I got HUF PAN in 2010, mentioned date of incorporation as 2008 (date of 2nd marriage). In HUF deed, I mentioned 4 members only (myself, wife, 2 children in 2nd marriage). I.e., I didn’t include the son from 1st marriage in HUF deed. My father gifted his self-acquired house to my HUF in 2018. Now he is no more. The son from 1st marriage is 23 years old now, he is demanding share in my father’s property saying it is ancestral property so he has a right in it. During a family panchayat, he got to know that house was gifted to HUF few years back. Despite that, he is insisting his right to get a share of that property and is threatening to file a court case for the same. To understand whether I safeguarded the HUF property well to my 2 children from 2nd marriage, I inquired different lawyers in Hyderabad, and got conflicting answers: 2 lawyers said that 1st marriage son doesn’t has right in HUF assets since he never stayed with me. But another lawyer said that all my descendants are automatically part of HUF, so I can’t exclude my 1st marriage son from HUF and I should have mentioned the HUF incorporation date as 2000 (1st marriage date). So looking for decisive answers to this scenario from experts here: 1. Is it correct to mention 2nd marriage date in HUF and only the descendants from 2nd marriage as co-parceners in it? If not, will HUF become invalid due to that mistake? 2. Does the son from 1st marriage have a right in HUF property, though his name is not there in HUF deed, but because he is a lineal descendant? 3. If son takes the matter to court, does he has a strong case to win? Will court grant interim stay order against selling the HUF property? Thanks!