My parents are angry I proposed to my girlfriend and it's because my sister isn't married

I proposed to my girlfriend and my parents did not react the way I hoped. They have always gotten along with her and said how much they like her but when I told them we were engaged they weren't happy. I have an older sister (I'm 29, she's 34) and my parents weren't happy about my engagement because they were hoping her boyfriend would have proposed by now. That's the whole reason they are upset.

My sister and her boyfriend have been together for over 10 years. They have 2 kids. I have no idea why he hasn't proposed after so long but it's none of my business. The way my dad was going on after he found out about my engagement made me think my sister's boyfriend was planning a proposal. I don't think that means I shouldn't be allowed to propose but my dad has admitted there was no plan for my sister's boyfriend to propose as far as he knows. When my sister found out about my engagement she actually cried and she isn't happy about the news either.

My parents told me they like my girlfriend, but my dad says we should have waited until my sister was married. I told him this is ridiculous. In January my girlfriend and I hit the 3 year mark. Even if my brother's girlfriend was planning to propose (he hasn't said anything to that effect) I don't see why this means I couldn't propose to mt girlfriend. My sister is an adult with a job so it's ridiculous that my parents are acting like she is trapped in a corner and can't speak up for herself. I also told my sister she needs to grow up after she threw a tantrum over my engagement and needs to talk to her boyfriend if she wants marriage, not tell me how unfair it is. I'm not going to let my family ruin this for me or take back my proposal like my parents suggested. I live in a different province so I can avoid them since they are acting this way. I just makes me angry the way they are acting like this is unfair to my sister.