Of course we want the best for our loved ones don't we? You may be a person who likes to 'solve' problems for others? I used to be like that
but have learned to listen, advise if necessary but not to take it as an insult when people don't take my advice. Are you the person they turn to for advice, a listening ear ......... ?
14 years is a long while. Are there children involved? Even if there is 'someone else' that is up to your daughter. How do you know her partner will be 'devastated'? Is this your view or has he told you in the past? Try not to put your feelings as if they are someone else's
Positive - your Mum is being cared for and appears to be doing well; your sister and boys have settled into a new life-style.
The thing I advise is for people who are asked to be the listening ear, go to the various support agencies and gather information which can be passed on; i.e. Citizens Advice, Relate, where will your daughter live if she leaves the partner ........ you cannot heal others, but advice and a listening air can be invaluable.