need advice now!!!

Okay so my ex boyfriend split up with me 4 nearly 5 months ago, and me and his friend have been talking, it didn't start of as anything serious as he was just being really good and was just being there for me. We've been talking for about a month and have both agreed there's feelings on both sides. We've had 1 on 1 time and we get on so well and I haven't been this happy in ages and he feels the same. We want to take it further but as our friendship group is quite close we're both worried how people wil take it, and I need advice on how to tell people what's going on. Help please☹️