There is no hard-and-fast rule on this matter. It is generally felt
that the bride's stepfather should not dress more formally than the
natural father of the bride. If the bride's natural father is wearing
a tuxedo, the stepfather of the bride may want to wear a dark-colored
suit. Some experts suggest that the bride's stepfather should dress
similarly to the groom's attendants, or similarly to the groom's
father, if he is present. If the stepfather is not an active member of
the wedding party (meaning that he does not walk the bride down the
aisle nor participate in the ceremony), he may wish to choose attire
similar to that of the wedding guests. But ultimately, the decision
should be left to the bride.
Here are some online references:
"Question: Should the stepfather wear a tuxedo or is a dark suit more
appropriate. The father will wear a tuxedo.
Response: The bride should make the decision, but usually a dark suit
Wedding Palace: Wedding Experts
A question from the mother of the bride:
"What should my husband (who is not the bride's father) wear to the
wedding? Tux or suit?"
"If the fathers are both wearing tuxedos, your husband can wear either
a tux or a dark suit, whichever he prefers. If the father of the groom
isn't wearing a tux, then your husband should not wear one either."
"If there is a stepfather involved in the wedding ceremony, he should
be dressed in similar attire to the groom's attendants. If he will be
present but not involved in the ceremony, he may dress similarly to
Creative Listings: Gowns and Formal Attire
"If either the bride or groom has a stepfather that they feel close to
that will be attending the wedding, it would be appropriate for them
to be included in the style of attire chosen. He may decide to dress
as the male members of the wedding party, or he may choose to dress as
the other guests do. He should also be presented with a boutonniere."
2 Become 1 Weddings: Wedding Attire Tips and Advice
A question posted in a wedding-related newsgroup:
"My mother asked what her husband should be wearing to my wedding. I
really did not know what to tell her was appropriate. I just said
'whatever he is more comfortable with.'
My mother married Bob when I was in college. I am not close to him at
all. I refer to him as my mother's husband instead of my stepfather.
Should he be wearing a suit or can he just wear slacks and a blazer.
He will not be part of the ceremony, however, he will be escorting my
mother into the reception."
"People who are not in the wedding party dress in the same manner as
guests. If you expect male guests to wear suits, he should wear a
suit. If you expect male guests to wear slacks and blazers, he may
wear that. If you secretly expect male guests to show up in jeans and
polo shirts, but you're hoping 'family' will dress better than that,
tell your mom to put him in slacks and a blazer."
From soc.couples.wedding newsgroup
Here's a different viewpoint, recommending that all the fathers should
dress similarly to the groom:
"Q: My parents are divorced and have both remarried. Both sets of
parents and my fiancÚ's parents are paying for the wedding. How do I
word the invitations? Does my step-father wear a tux?
"A: ...Does your step-father wear a tux? Yes - he is a participant in
the wedding party (he is helping foot the bill) so ALL three dad's
should be in the same or similar attire as the groom. Traditionally
the father of the groom doesn't 'dress up' because he isn't a member
of the wedding party - not so in this case. You are truly going to
have a 'family affair' and everyone should get equal billing."
Google search strategy:
Google Web Search: "wedding" + "stepfather" + "attire"
I hope this helps. If anything is unclear, or if a link doesn't work
for you, please request clarification; I'll be glad to offer further
assistance before you rate my answer.