Wow!
Agreed your MIL is lashing out and her upsetting your child needs very firm dealing with.
That was crossing a line that I wouldn't tolerate under ANY circumstances.
However your FIL is truly the scum of the earth.
Your poor MIL has been betrayed in the most heartbreaking way and must feel so devastated and fearful.
Words nearly fail me.
You are a young woman OP, I suggest you take a long hard look at that man you married.
He sounds of similar character to his father, that he could stand by and engage with a father that would do that to his mother.
Unbelievable.
Loyalty isn't his strong suit clearly.
Look at your own children and try and imagine yourself 30 years from now and how YOU would feel.
They share DNA, and the apple often doesn't fall far from the tree.
I am so glad that despite loving my husband deeply, HIS morals do not dictate MINE.
Your FIL is a truly awful excuse of a man, and I wouldn't want him near me, and my husbands views would not dictate mine in a similar situation.
That your SIL would want a father like him involved in her wedding, when he has made such a mockery of the vows he made to her mother, is really sad.
I would be looking at my husband very differently knowing he is so quick to move on from such horrendous treatment of his mother.
I'd also be very nervous of ever getting ill🙄