My boyfriend's children
I am 35 years old, never had children and living in Europe. My boyfriend, 42 years old, with whom I am dating for over a year now has two kids from two different mothers. The first one is an 18 years old girl and the second one is a nearly 5 years old boy.
With the 18 years old girl, I have established a friendly relation which resembles the communication between two sisters. She stays over at her father's 2 weekends a month.
The 5 years old boy stays at his father's one week in every 2 weeks. I have met him just 1-2 months after starting dating his father. Although I thought it was too early for meeting him (both for him and for me, too), his father insisted and we built a nice relationship. Neither the boy(to my knowledge), nor I have any complaints. Our relationship is built on a lot of games, sharing responsibilities together (brushing teeth, setting the dinner table etc) and we are having a lot of fun. I always call him my "small friend". I love him so much and I know I am not his mother, and I try not to play that role. I also met his mother via telephone and later face to face. (For the telephone conversation, the boy insisted when he was talking to his mom that I should talk to his mom. We did.)
My question is regarding my responsibilities and limits in this relationship with him. I love him so much and I don't want to make any mistakes which could have negative impacts on the development of his personality. Please help. How shall I interact with him?