Elderly Mother in Law

Ease her into it gradually.

Perhaps you need to have some event to go to together one Sunday, so that your husband will have to miss his visit to his mother that day. You could join him on the Saturday, to double up the companionship and help do the chores and shopping, and arrange for someone to visit on the Sunday - one of your husband's brothers is a good candidate!

While you are there, you could compile a list of what your husband does for her, and work on how it could be done without putting so much on to her. Involve outsiders in one aspect after another.

Plus, while enjoying the event, you would be able to tell him how much it means to you to be spending time with him, instead of on your own. Then keep organising more things to do together on a Sunday, while MiL is cared for by others. She will probably enjoy their company once she gets to know them.

Typo - " without putting so much on to HER" should be "onto HIM"

The four brothers could visit her on one Sunday a month each and still have three Sundays each for their own families. Surely that isn't too much to ask, when one of them visits her several times a week?

In a similar situation I got involved with accompanying my husband to his mother's to help clean.
Its not a good idea. Your resentment grows and grows when you see the old lady exploiting her son and manipulating him.
We eventually got her a carer but we called her the 'district nurse'. She wasn't from an agency and cost a lot of money but she understood the situation. She only came once a week for 2hrs on Thursdays and helped her to shower and checked her many pills and tablets. Then she'd sit and chat over a cup of tea.
Husband still went over on Saturdays, but phoned her every morning to make sure she was OK.
But I rather think, from the sound of your letter, that your husband wants to go, likes to go, and is unlikely to stop going.

If you DH was the favoured son of three then sometimes that turns around to bite you in the ass!

My sister was the golden child when we were growing up. She often got me punished with her whining and snitching. Later when my father had died and my mother became very clingy and dependent my sister found herself neglecting her own family and being called round every day. Sometimes she would just get home and mum would call her in tears for some minor happenstance or just because she felt miserable.

By then I lived in another city, had a full time job which involved frequest trips abroad and did not drive. So of course I was conveniently "not available". When my sister complained I told her that she was paying it back now for being the golden princess.

Can't the grandchildren be more involved with visiting her?

The husband does not need to spend all weekend caring for his mother; he is choosing to do it. Every suggestion for help, support, care has been rejected, apparently by the mother, and I doubt very much that the other two brothers will step in and share care. They can see how their brother is being used, or is possibly using, his mother.
My father cared for his mother for 44 years until she died aged 94. His father had died when he was 21, and he lived with his mother until he married aged 38; as far as his mother was concerned her life wasn't going to change because her son had married. He continued to support her practically and financially until she died, and it caused endless trouble between my parents and spoiled their marriage. His brother, the golden boy, refused to help because he thought my father was a fool for doing all he did, and stayed well away.

I am sorry for Piperly, but the situation does not look promising. Her husband should not be so exhausted by helping his mother maintain her flat every weekend that he falls asleep every evening; my father used to spend every Friday night and Saturday morning with his mother, and that was to maintain a three bedroomed house and large garden. I suspect there are other forces at play here. Piperly needs to go with her husband and see exactly what he is doing, or expected to do.
And sometimes dear little old ladies can have a will of iron.

My husband showed a wonderful caring side when his parents got too old to manage. He was one of 6 but the most loyal. They placed their confidence in him and I was proud that he did it. After his father died he sat with his mum every night and they watched tv. She too died but he had done his best and after all our parents looked after us. I can understand how it’s hard when you haven’t been married very long but before you know it the situation will change. Be proud of your very caring husband.

I just feel really sorry for Piperly
and i didn't see why she should have to join in cleaning the flat for a woman that didn't really want her there. She is already doing everything in their own home.

I never get this idea that because parents looked after their children then children should return the favour to the detriment of their own lives and relationships. Decent caring parents would not want that, in my opinion.

This is very much an individual people thing. Could you set aside time for a date night or afternoon outing and explain why you are doing this? I looked after both my parents and father in law over a ten year period and had to literally force time with my husband and children or else I would have become exhausted.