Relationship

My boyfriend of almost 4 years just turned 18 on the 8th and I’m 17 I’ll be turning 18 on August 10 and my family thinks it’s a problem because he’s just like 2 months older than me they want us to break up and get back together once i turn 18 but i don’t understand how it’s a problem for us because we’re just months apart and my brother is 19 and dating a 16 year old. I get annoyed when they ask my boyfriend if he’s gonna break up with me or if we’re just friends I don’t know what to do. any advice?