Is it ok to give my cousin a blowjob?

So my cousin and I have been really close since we were young. He is 7 years younger than me. In his 20s. I’m out and make no apologies for who I am. No I’m not a flamer. He is “Straight”. He has a 10inch penis. We were driving to the next town about 5 years ago and he undid his fly and pulled out his hard Wang, while he was driving. This isn’t uncommon he’s that bloke that gets it out whenever possible. He said that he has never had anyone ever swallow it whole. I joked I bet I could. He told me to try. And I sucked all 10 inches down while he was driving. I had his balls on my chin. When I came up he was dribbling and asked if I could finish it off. I opened my mouth and sucked him until I had a stomach full of baby batter. Ever since then when ever we have a spare 10 minutes he asks for a quick gobby. Ok so. My question... is it ok to give your cousin a quick blOwjob? If I’m honest i fucking love it. Is this normal? He says I suck cock like no one else can. Am I alone with this? And is there any harm in doing what I do best to a blood relative..?