I would argue that cohabitation is equally disastrous for step families - and in the long term, even more so.
Bearing in mind that this thread is about making sure people are aware of their rights and best interests - rather than insist everyone get married - and is aimed at the standard cohabitation set up where Male partner is working full time and Female is either a sahm in order to facilitate childcare to young children or in low income part time employment to slightly older children. The home is in his name.
If you look at the above scenario and imagine the couple break up. After a few years of being a single mum and receiving sporadic child maintenance, (Which was her only entitlement as no claim on a house) the woman meets a man who is also separated. He was also unmarried but has two children who live with their mum.
The mother in our scenario is surviving on tax credits and part time work in rented accom. Not well off but not on the breadline. All she has , is hers. Now she moves in to New boyfriends home. She loses tax credits and her home but that's ok because new man is kind, good to the children and treats everyone well. He shares his income. He pays maintenance. When the children reach Secondary school she ups her hours to full time. She starts to pay the bills while he pays the mortgage. Boyfriend able to save some money now she's doing this. She is still low paid so paying bills is most of her money and nothing to save.
After 20yrs together, he drops dead. No Will. Law of intestacy doesn't even list 'partner'. The estate including the property she lives in belong to the two children. She is homeless.. with only the small savings she has managed to save since the children have left home.
This is a pretty standard scenario for a second relationship. Marriage is the same protection for the lower income earner as it is for a first relationship. The only difference is the MORAL issue of the fathers Estate going to the stepmother , who could then leave it all to her children bypassing his.
I would suggest it is ESSENTIAL to get married if you are in a second relationship with children each but not jointly if you are the lower income earner and do not own your own home OR both.
I would suggest it is ESSENTIAL you don't get married if you own your own home and want it to go to your children in entirety and not your spouse until you have taken legal advice on 'assets amassed before the marriage ' which can be ring fenced.
However like RileyW I married because I wanted to. DH has children as do I. None together. We both bought money from our divorce to the purchase of the property so that's straightforward because we have a legal agreement whereby DH has left 'his' half to his children as have I. However they only get this when we are both dead. If DH dies first his kids can't force me out to get the money and vice versa if I die first.
Our cash is in separate accounts and left to each other and children in individual bequests.
My pension goes to him.
My lump sum goes to my children
His pension goes to me
His lump sum to his children.
If we didn't marry the pensions simply end when they die. It's a spousal pension (married and civil partnership only) NOT a partner pension.
The house situation wouldn't change.
Marriage would have no other effect on the Will as Wills can be changed without a partner or spouse knowing.
Ultimately its the pension situation that has the biggest effect but having paid in all my life I want this for my husband should I die. With all things considered , it is the Pension that makes marriage essential for second marriages as this is something often only payable to a spouse and is simply lost if there isn't one.