Lord Muruga, as I read once, was one of the 4 Sanatkumaras originally. That, when asked by Shiva-Parvathi if he would like to be born as their son, he replied that yes he would, but devoid of any association with the Uterus. Therefore eventually he was born without sambandha of the uterus, in the form of 6 flames from Lord Shiva's 3rd eye.