Hopefully the spouses will be at the head table and you won't be alone. If you aren't then the seating is the responsibility of the host and they should make sure you are assigned a table with people who you have something in common with and can enjoy yourself. During the reception line you can just find your seat and order a drink if you aren't comfortable mingling. Since your hubby is a groomsman you should be on the bride's and groom's families' radar and they, knowing you will be alone at some points and don't know anyone, should make sure you feel comfortable. It is your responsibility to be friendly and upbeat and it is the host's responsibility to, as much as they can, make sure their guests are comfortable and enjoying themselves. Your husband might even know people he can introduce you to who you would like hanging out with. Hope you have fun. Just wear a fabulous dress so if you aren't having fun, at least you'll know you look gorgeous.
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"If you have men who will exclude any of God’s creatures from the shelter of compassion and pity, you will have men who will deal likewise with their fellow men." — St. Francis of Assisi, 1181-1226