One (so-called) sexual "fetish" or paraphilia is "foot fetishism" (also called "foot partialism," "foot worship," or "podophilia"). Foot fetishism, foot partialism, foot worship, or podophilia is a pronounced sexual interest in feet. It is the most common form of sexual fetishism for otherwise non-sexual objects or body parts, and is more prevalent in men than women.
Toe sucking (along with finger sucking) is a behavior that infants often perform on themselves as a form of self-soothing and self-play, and that can also be a form of stimulating sex play between lovers.
As foot fetishes are fairly common among males, there is a large number of BoyLovers (but a small percentage of BoyLovers) who are foot fetishists.
In 2003, Trenton Velches (who apparently has a fetish for young boy's feet) was sentenced to life in prison for sucking on the toes of about 20 young boys. The court held that this constituted assault and lewd conduct. There was no contact with any other body parts of the boys.
According to the Web site of the California Department of Corrections & Rehabilitation, he is currently imprisoned at California State Prison Corcoran.