Since Paul mentions that the cabin was his mother's and that he misses his father, it is likely that his parents are dead too.
Paul most likely had a good relationship with his wife.
Later, Rachel starts to worry about her relationship with Paul because of how private he is.
She tells him that she wants to know more about him and he tells her about the time that he was six and his parents bought him a "plastic chicken you hop around on" instead of Big Wheels like he wanted.
" and when Rachel tells him Paul was looking for his keys, Ross incredulously replies "In your mouth?! Throughout the rest of Paul's appearances, he and Rachel were happy together, until the former's last appearance when he starts crying incessantly about his miserable childhood.
" obviously showing disgust at the sight of Paul and Rachel kissing; so Ross was presumably happy when Paul and Rachel broke up. The two first meet at Central Perk while Paul is trying to find his keys and Rachel soon finds them. Rachel eventually gets him to calm down and they have sex, but Paul soon can't keep himself together and starts crying again, causing Rachel to break up with him.
It is apparent that they were very neglectful of him and did not show him much affection, which is most likely why he is so overprotective of Elizabeth.
It seems that he had a good relationship with his sister before she died, due to his sad look when speaking of her with the gang.
Coincidentally, Ross showed obvious signs of jealousy like when Paul left him and Rachel at her and Joey's apartment, he kept asking "What the, how did...?
He reveals that kids made fun of him and even called him 'Chicken Boy', making him a very insecure person.
He begins crying for hours, revealing more about his childhood to Rachel.
When Chandler walks into the room, Paul asks Chandler if his father ever hugged him, causing Chandler to reply "Did he ever hug you? However, Paul still asks Chandler to hold him, and when Joey walks into the room, Paul runs over to him and lifts him off of the floor while hugging him, too.
Rachel finally gets Paul to calm down long enough to have sex.