I [23F] am in love with my dungeon master [22M] who is a family friend my family told me I cannot date

My dungeon master is a family friend who I met in passing over a few times the last ten years, but did not start spending significant time with until recently. Our older sisters have been friends for 10+ years, and I am close to his sister. The two of our sisters have always wanted us to meet thinking we would become extremely close friends because we have a lot in common. We started a DnD campaign about two months ago. Our party consists of me, my sister, her best friend, and him as the dungeon master. The instant we met I felt like he and I really hit it off. He and I have similar interests and joke around really well. I started calling him regularly as friends, and we could talk on the phone for an hour or two at a time.
I was dating my ex for about 2 years and I broke up with him a month ago. Since then, I realized some of that was motivated because I got along better with our DM than I did with my ex. I was the one who broke it off and I feel extremely happy and relived with it. I don't think me wanting someone else is due to me being sad because of the breakup, because I am not sad.
The DM and I are friends, and he is even going on a vacation with him, me, my sister, and his sister soon. I admitted to my sisters boyfriend I have feelings for the DM and since then my sister has explicitly told me I am not allowed to date him, only be friends with him. She worries if we date and break up it will strain her relationship with her best friend.
However, I literally cannot stop thinking about him and I have butterflies in my stomach. Recently, a family member was diagnosed with a serious illness and he was the first person I called and he talked through me crying. I feel like he is interested in me and we have made plans to hang out one on one. However, I do not know how to bring up this topic since we hang out for DnD about once every other week and it will make things very awkward for everyone if we start dating. I don't even know if he likes me in that way and if he doesn't it would make it that much worse.
TLDR: My sister explicitly told me I cannot date him because if we break up it could jeopardize her friendship with his older sister but I have never felt this way about anyone before.


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