My husband and his "cousin"....

So a little back story on the situation. My husband has these cousins that aren't actually related at all. The wife and younger sister are beautiful. A while back when me and my husband were only dating I find a pic of three girls in their bikinis his "cousins" and one of thems daughter..he said she sent the pic to him because her daughter wanted to say hi.. -__- I brushed it off but it still stuck in my head as being weird. Later on the younger cousin texted him all flirty like telling him how cute and funny he is. He told me don't worry about it she's young , she's my cousin blah blah . This "cousin" blocked me on social media and didn't like me from the get go..for no reason before we even met. So today I'm looking at my husbands pics in his phone ..he's a cake decorator so he usually takes pics of the cakes me makes . He made one that said "Hi Julisa" which is the daughter of his "cousin" the pic was in his deleted photos so I snoop further finding he messaged the cake to the "cousin" on Instagram ..the Instagram he's never on..is this weird or am I overreacting?