If it means people are in a non-monogomous relationship, the Clintons would be "gay."
If it means being in a sexual relationship not for the purpose of having/raising children, then John Kerry and Pat Buchanan would both be in "gay" marriages.
If it means not being married, then Condoleezza Rice is acting "gay."
If it means being unmarried and having lots of sex, there are plenty of straight men and women who act like that. Are they practicing the "gay lifestyle?"
What is so different about the "gay lifestyle?"
Is the lifestyle itself so different, or is the only difference the genders of the people having sex? If that's the case, then there is no such thing as a "gay lifestyle." There are straight and gay people who have different lifestyles, but none is specifically straight or gay.