Would this upset you?

My sister got married in July and is trying for her first baby! She has a miscarriage but they are trying again and I couldn't be happier for her. Ive been with my boyfriend for 5 years and we are moving in together next month. We've talked about getting married and he said that we will probably get engaged shortly after moving in together. I told this to my parents and they all said "you can't, we need at least 3 years between you and your sisters wedding, and she's going to have a baby soon and that's expensive" and she was being completely serious. I get it. Weddings are pricey but why should I have to put my life on hold because my sister just got married and is planning for a baby. Why do I need to wait to take my relationship with the man I love and want to spend the rest of my life with to the next level. I feel like my whole life I've been second to my sister. "Oh you cant because your sister needs this" ... "oh it's -30 Celsius out and you want a ride, can't cause your sister is over" etc. Like it's obvious there isn't equal treatment. But why am I expected to put my life on hold and my future on hold? It's not like I'm asking for money or anything.