It has been 8 months and I have not met his kids. Should I be worried?

He has been divorced almost 2 years. His kids are ages 13 and 15. His son wants to meet me (age 13) but daughter says she is not ready. I am 34 and have a 13 year old daughter. He is 38 and I consider him a good father and a good person. I love him very much and do not want to force him to introduce me to his kids but at the same time I feel that maybe it is too soon forthem. Part of me wants to walk away but I am torn. Am I being unreasonable? Hetalks about marriage with me all the time and I have met his friends and family