My bf finds out that he might have a 3 yr old son

My bf goes to drop off food to his 1 year old daughter's house. His daughter's mom shows him a side by side photo of their daughter and the 3 yr old boy. She said the mother of the son messaged her on Facebook saying that they might be siblings. So my bf talks to the lady his tells him she wanted so long because she was scared to tell him and In denial of him being the father. He told her why didn't you tell me when i continued asking even after saying another man was the father. I saw pictures and they for sure all 3 have similarities. He asks me how do i feel if the baby is his but i didn't have an answer. I'm more so just getting more and more depressed about if ill have the opportunity to give life to my own child. But i hopefully dont know what to felt, I'm still going to be there like i am with his daughter.