Back before society turned fake and gay, it wasn't unusual for fags to hide their faggotry by getting married, having a couple kids, and sneaking away to have lots of gay affairs. This is also one of the major ways aids spread to straights.
So you never heard of this? Guys getting married having kids and then suddenly deciding they're fags? It's a thing. DeNiro's dad took off after he was 2 years old. Told everyone he was homosexual and left. His mom had to raise him on her own, which explains a lot.
Because fags used to be forced to act like normal human beings and married and had kids, and its also possible he was straight but developed a porn addiction that made him a faggot.