7 year old step child help

Hello, my best friend just got married and her and her now husband were not expecting full custody of his 7 year old. This was very unexpected and happened a month before their wedding! She never wanted children, But had already resigned herself to summer visits and holidays, Knowing that was part of the man she loves, But not full time mom. Anyone have any tips and suggestions or sources for information. I myself am not a mom and can't imagine the stress and struggle that would be. He's a lovely child and very loveable. But any help is always welcome. I want to be a support, but I lack experience in that field.