I have been with my boyfriend for over 3 and a half years now. As with every couple we have had our ups and downs and major issues but we have managed to work through them every time. The one and only thing that I am uncomfortable with is his family. They are perfectly nice and have never been blatantly rude, but I know that they have never accepted me.
My boyfriend and I come from completely different backgrounds, so I slightly expected this, but I figured it would not still be a problem nearly 4 years in. I am a part of a very large family and they hold a major role in my life. I hoped that one day his family would accept me as my family has done for him, but I just don’t see it happening. I know that I am in a relationship with him and not his family, but I am still worried. I have brought this up to him multiple times and he thinks that I am overreacting.
Since we do plan on getting married in the next couple of years, at one point his family will become my family. I am just afraid of having such a negative connotation around the concept of family when it comes to them. I simply do not know how I should go about addressing this and any help would be very helpful. Thank you!!
LemonVibe 
This is more of a problem with them than you. Do you know what it is that makes them not accept you? Perhaps they are worried that you will break up with him and leave him heart broken since you’ve had ups and downs? Maybe no one is good enough for him and they won’t accept anyone.
If your relationship with him is strong enough you will be fine. How often do you even have to see them?
Best wishes to you both.
Honestly, I know this situation and it is more about them and whatever hangups they have then about you. Just don’t let it get in the way of your relationship and if you get married maybe they will get over whatever it is. If not, then that is for them to figure out.