Peter and Grace have black hair, brown eyes and tan skin. Usually, Peter wears white shirt and a black jacket, and Grace wears pearl earrings and a white dress with purple flowers on it.
From dialogue with Kaitlyn, we are given the impression that Peter is a very strict and traditional parent. He is extremely upset when Kaitlyn accidentally comes out as lesbian to him and Grace. However, in Book 4, when visiting the Liaos' home in Texas, it's shown that Peter is trying his best to be a supportive father, as he has purchased a set of cups that read "LGBTQ+". Naturally, Kaitlyn is embarrassed by this.
Grace is presented as a traditional mother who loves her daughter. However, she's taken aback upon finding out Kaitlyn is lesbian, but accepts her nonetheless, and encourages her less supportive husband to give their daughter a chance.
Kaitlyn is Peter's and Grace's daughter.
Peter sees in Arjun the perfect son-in-law and always tried to matchmake Arjun and Kaitlyn. Grace also likes him very much but because she knows that Kaitlyn is gay, she's probably never seen him like that.
Before they even met Your Character, Kaitlyn already told Peter and Grace a lot about her.