My father died a few years ago after a long illness. At the time of his death, I had a toddler and was heavily pregnant with DC2 and so I focussed on the birth of my child and to be honest, I have never really let myself grieve for Dad, at least not properly. Not a healthy coping mechanism, I realise, but this is how I have dealt with it.
My mother is a wonderful woman and she and my father adored each other, though she lived very much in his shadow and depended on him a lot. She was devastated when he died but I am so proud of the way she has got on with living her life, doing things she never did when he was alive, due to lack of funds when we were children, and lack of confidence in herself. She now travels abroad with friends and family, volunteers for a local charity, and is active in a number of groups in her village. I live a few hours away from her but she travels to visit me regularly, and my husband and I take our DC to visit her several times a year also. I have other siblings who live closer to her and we are quite a close family, and mum likes to help us all out as much as she can with childcare etc. I have always hoped mum would meet somebody else, as she is only in her late 60s, fit and healthy, and has, I hope, a long life ahead of her. And what do you know, she has! Someone she has known almost all her life, someone we as a family all know quite well, has apparently been working up the courage to ask her out for a couple of years and finally, they have started seeing each other recently. It’s all going really well, they are getting along famously, and we genuinely couldn’t be happier for her. She’s like a giddy teenager. 
But here is the AIBU (eventually, sorry!). I am hosting a family celebration in a couple of months, it’s quite a significant one and one that I know my father would have enjoyed. There have, of course, been numerous family occasions since his death, and at all of them, I have had a fleeting moment of wishing he was there and then putting it out of my mind (bottling it up as always). My mother has, of course, been on her own at these events (i.e. no partner), and that has made me sad, so naturally she wants to bring her new man to this event. I have encouraged her all along to be open to meeting someone and I am delighted she has, but I feel so unsettled at the thoughts of him being at this event. I am happy for her, but I feel so sad for me. I know this is selfish and probably childish, and I will of course welcome him and not make him feel left out or embarrass my mum in any way. But AIBU to feel overwhelmed with sadness at the thought of him being there, as if his presence magnifies my father’s absence in a way that has never been apparent before when it was just my mum on her own? I feel as if all the years of grief that I have bottled up since Dad’s death are about to burst out and I really want to get a grip of myself before this event. What do I do? My sister is a big advocate of a good cry but I’m afraid to start crying as it never makes me feel better. I don’t want to make my mum feel bad and so I think speaking to her is out of the question. All advice (and kicks up the backside) gratefully received.