How to tell a long-time friend I'm not interested in either talking to or dating him?

For context, my (35f) husband passed away last May. All these guys have been coming out of the woodwork now that a year has passed. My best friend's younger brother (33m) started sexting me last night and I need to tell him I'm not interested. For one, he was close with my husband, and it pisses me off more than I can say that he's now trying to get with me. I'm not sure how he viewed my husband, but I know my husband viewed him as a good friend. He is not being a good friend to my husband.

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Any advice on how to have that conversation with him? He tried to sleep with me a long time ago, after I broke up with my ex before my husband was even in the picture. I have to see their family all the time, so he's now made this very awkward.

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Any advice is appreciated!