Not unless she's paying for the wedding - and even then it would be tacky. Only invite her close friends...and then pay for the wedding!
NO
First, you should get permission from the bride to be and your brother as to whether you can invite your friends to the wedding and let them know how many of your friends you are inviting. Weddings are extremely expensive and at the reception the food from the caterers is calculated by 'plate settings' which can run from $25 per guest and up. If you have had permission then you would get the invitations from the bride and fill them out and mail them asking the bride for help if you are stuck in filling the invitations out.
Yes, traditionally one side of the church is filled with family and guests of the bride and her parents, and the other side with the family and guests of the Groom .
The bride should discuss with her biological mother how she would feel if her ex husband's common law wife was invited to the wedding. If the biological mother is comfortable with this then there is no reason not to invite the common law wife. If the biological mother is dating someone special or is remarried and bringing her mate to the wedding then you should ask your father and his common law wife without discussing it with your mother.
It is in poor taste to have a bridal shower at the home of the bride's mother. The bride's aunts or friends host showers.
It is up to the bride and groom and one evening get both sets of parents and go over the list of guests everyone wants to invite. If the grooms parents have more guests then let them know straight out they will have to pay for each over the limit guest's 'plate' (caterers at reception halls charge by the plate.) This is the only fair resolution and the groom's parents should agree to this as they are not paying the whole bill for the wedding; the bride's parents are.
everyone the bride and groom invite
How to toast the mother of a bride
The Mother of the Bride CAN wear black---but it would be very poor form. People at weddings should be wary of black.
I think that it is more usual for some friends of the bride or groom's parents to host a shower or some of the bride's girlfriends but it is not improper for the groom's mother to host one if she would like. If there are other showers being given, I would not do another one if I were the groom's mother. It is nice to have the groom's mother and the bride's mother just enjoy the showers as guests.
No, it is not alright for the groom's parents to not invite their friends. Generally the bride and groom's parents along with the bride and groom sit down and go through the list of guests. There are certain people that can be left out such as out of town friends or acquaintances of both sides of the family. If children were going to be asked to attend then leave the children out and just ask the parents. This will cut down on your list. If this is not good enough and you can't cut down the list enough then you should go for a smaller wedding (chapel style) and spend the money on having the reception. Receptions can be held at either the groom or bride's home or any town hall and the bride, groom and wedding party can help to decorate it. This will save a lot of money. Food can either be made by relatives or fingers foods can be served by caterers for an afternoon reception.
A wedding toast to the bride's mother is sometimes made by the bride. She will thank her mother for all she has done for her.