My partner get jealous of my family?

My family is very tight knit, my mothers very close with her sisters and all us cousins are very close. Recently, we had a family gathering just to catch up because we hadn't seen each other in a few months so my partner, my son and I went along and it was so good to see everyone! My eldest cousin was my protector growing up, he would save me from al the bully's and he would always look after me so we have a pretty special bond. He just got out of jail so I hadn't seen him in like 3 years so naturally when I saw him I ran up to him and gave him the biggest hug and he kissed me on the cheek it was just sooooo good to see him. 
Later when we got home my partner was in a bad mood so I asked him why was wrong and he said it was weird that I was so happy to see my cousin and he was disgusted and I'm never that excited to see him. I tried to explain like I hadn't seen him in years and we were close. I think it was just because he hadn't met him before maybe? Anyways he hasn't talked to me for three days because he's still upset about it and I just don't know what his problem is... is he jealous or is he genuinely disgusted that we are as close as we are?