DF and DM seperated 15 years ago and dont live close to each other. We all get together for Christmas and other family occasions and parents get on fine but they don't keep in touch. Since they split, parents have never spoken of other partners until now, DM has a new partner who has lived with her since earlier this year having met shortly before. Another family member is due to get married and both parents are invited as well as DM's new partner. As far as i am aware, no one has ever mentioned DM's new partner to my DF. None of my siblings nor I have met him so it would have felt odd and gossipy. I feel like someone should tell my DF before the wedding though.
Not sure if im making a mountain out of a mole hill.
1.do nothing its not my business.
2.tell DF myself.
3.ask DM to tell DF.