Mother In law treating grandchildren differently

[Chariotofflowers]

My step daughter is 7 and my baby son is 9 months.
For background: my husband and his daughter’s mum were never in a relationship, it was a young drunken fling but they co parent well and I get on with her well too.
We have been together for 6 years and married for 3. I have a great relationship with his daughter and we have her 50/50.
So my issue isn’t with any step parenting on my part, as I know often step mothers get blamed, but my issue is with favouritism between both children.
My mother in law in particular is the worse for this. We have a great bond and get on well so I don’t want to jeopardise that by calling her out on the difference in treatment. She has always favoured step daughter anyway as her only grandchild until our son was born. I thought when our son was born she would give 50/50 attention but this hasn’t happened. Our son is ignored, she barely holds him and has never played with him. She spoils step daughter with any toys and clothes she likes, takes her to the park and soft plays, and generally treats her better. She tries to hide that she does this which to me shows she knows it’s unfair. Her sisters and their children (husbands aunts and cousins) haven’t even met our son. They’re a close family so I’ve always found this odd, but they have avoided any opportunity to meet him despite living local. They make effort to visit mother in law’s when step daughter is there and will gift her toys, sweets and money.
They had a family party planned but they asked for step daughter to come and for me and the baby to stay home. We were both puzzled so my husband asked her why she is leaving me out. She said she doesn’t want everyone holding the baby and ignoring step daughter. This has never been the case and she hasn’t shown any sign of jealousy when people hold the baby, in fact she’s a proud big sister who shows him off to anyone and even asks her school friends to come and say hello if we do the school run.
It upsets me to sit back and watch this divide knowing my son will grow up knowing his gran isn’t interested in him. I’ve spoken to my husband that many little things over the past few months have developed, and he has also noticed but thinks when our son is older it will even out. I don’t believe it will.
I know I can’t force her to be involved or treat them equally, but my main worry is that step daughter will begin to milk it for want of a better word and it’ll cause sibling issues later on. My husband and I treat both children the same and feel we’ve done well to prevent jealousy, this clear favouritism could ruin that later on.
I don’t think it is personal towards me as I don’t have any reason to assume they dislike me. They didn’t build a relationship with step daughters mum and only see her in passing so again no jealousy or resentment over my husband’s choices.
Is this something we should discuss with mother in law to nip in the bud or do I accept we have no control over her behaviour and let it go? How do I ensure my son doesn’t feel left out as he grows up? Any advice at all would be great

I would let it go. You don't want to sour the relationship over something which will likely change in time organically. Sounds like granny is over compensating so DSD doesn't feel pushed out by daddy's 'new family'. Also, some people just aren't interested in babies 🤷🏻‍♀️ DH should have called her out about the party though

I would say it’s all or none for the party.

but with such an age gap there is always going to be a difference in how they are treated so I wouldn’t read too much into things

Being generous, I assume that the family feel sorry for sd having divorced parents and overcompensate with the gifts etc

It sounds like your MIL is treating the kids differently and yanbu to keep an eye on this before your son realises this. You can't really say anything that's going to make her change things.

Family party =all or none. Being the favoured dc isn't the best for that dc either.. Damaging sibling relationships is a twatty thing to do. Nip this shit now. Your dh needs to stand up for both dc. They need to be seen as equally treated.

Mmm I think this can be a difficult one. 1) lots of people don't find babies that interesting. No conversation yet etc and perhaps they feel a little sorry for her in that her parents are together and over compensate.
See how it goes. I'm sure they'll be more interested in your baby when he is a little older. Not worth a big fall out.

I would guess she's over compensating as well. It can be hard for older children when there's a new baby in the home and a large age gap even if the parents are together. She may be doing it in a very clumsy way, but I don't think she is doing it to be dreadful. She will just want her granddaughter to know that she hasn't abandoned her and neither has her wider family, now that there's a new baby who is part of a stable family unit in town.

Hi OP,
I think the background is relevant as there is no reason to view you as the ‘new family’ when your DH never even was in a relationship with DSDs mum.
You are his only family.
You are her only daughter in law.
Not sure how to handle it now, however I would remember how you are being treated now for the future.

Agree that babies are not that interesting to some people & the things she does with SD are not really things your Ds could tag along on.

If you & MIL have time off in the day when SD is at school, how about trying to spend more time with her then so she can develop a closer relationship with your Ds?