That is a decision which belongs to the prospective bride and groom. But,....if the aunt was part of his/her life in any good way, then yes. Besides, more gifts right. ;)
NO
step brother
Your sister's aunt (who is also your aunt) is the baby's great aunt. The baby is a great niece or great nephew of your sister's aunt.
Step by Step - 1991 Yo-Yo's Wedding 1-7 is rated/received certificates of: Argentina:Atp
grand aunt
Anything you or the grooms parents feel comfortable with maybe a honeymoon present. If they step in too much just ask them who's wedding is this
Your grandfather's step-son would be your uncle, or step-uncle, depending on how technical you are getting. Your uncle's ex-wife would be your aunt, ex-aunt, or ex-step aunt, again depending on how technical you are getting. Blood-wise, she is no relationship, so it comes down to if you still want to consider her an aunt or not. If you still want to have that relationship with her, it is okay. If you don't, there is really no commitment.
Yes, he can. But he'd be marrying his step-aunt.
You might call your father's stepsister your step-aunt, but you might simply call her your aunt.
When planning a wedding, invitations are a two step process. Save-the-date cards should be mailed out four months in advance to let guests know about your engagement. The invitations should be sent out two months later leaving guests about 6-8 weeks to RSVP. When preparing for your wedding, the general rule is that save the date cards should be mailed out four months in advance. Wedding invitations should be sent out no earlier than two months before the wedding.
Your Aunt. With Aunts and Uncles there is often no blood relationship howerver they are still your Aunt or Uncle. With step families taking the role of step Grandman, Grandpa, Cousins Aunts and Uncles it is more of what the individuals feel comfortable with. If her name was Beth, you could call her Aunt Beth if you were comfortable with it or just Beth is fine. If they were step sisters before you were born and the family is close then she would be your Aunt since birth and no step class is really recognized. If you were older when the marriage took place then a first name is fine.
If your great Aunt adopted her step-son, then he is your first cousin once removed and his child is your second cousin (by adoption, if your like). If she did not adopt him, then his children are not related to you.