Not every child can give its mother a string of orgasms as it is born -- not when the echography shows that it is actually a couple of ischiopagus Siamese twins, and they could only be brought to life via a Caesarean section.
They were really beautiful girls, and were named Dionaea (the one at the right) and Cytherea (the one at the left), alternate names of Venus, and their beauty bloomed when they reached sexual maturity.
Their parents wanted to separate them, but image diagnosis specialists discovered that, although the girls had two backbones, two complete ribcages, four breasts, four arms, two heads (and two perpetually speaking mouths), they shared a single set of female genitalia.
An ersatz vagina could be surgically built, but the clitoris and the womb couldn't be split without spoiling them -- so separating Dionaea from Cytherea meant condemning either of them to anorgasmia, and either of them (not necessarily the same girl) to sterility.
So the parents left the girls conjoined, with a side effect they didn't foresee: a Siamese twin can't masturbate without forcing orgasm upon his/her sibling. So they had to negotiate when and how to have sex together, and managed to enjoy each other's company three times a day at least.
When they became 18, their parents bought them a motorbike, as it was easier for them to ride it (as they shared the butt and a pair of legs) than to sit in a car; it was also easier for them to alternately hold the handlebar (positioned opposite their navel) than to alternately hold the steering wheel (which was either at the left or at the right of the cabin).
But the parents didn't foresee that their children would also buy a set of Duotone Balls, so each motorbike ride, with its associated accelerations and decelerations, starts and brakings, turns and twists, was a supplementary orgasmic experience for them.
The girls had also to buy lots of wide plasters, because they were unwilling to remove the balls as they went to class, but the only way to prevent their classmates from leering at their erect nipples was to disguise them -- moreover, erect nipples are more easily worn by substandard lingerie when riding a motorbike or even walking a marathon.
Their family wasn't rich, but they were close relatives to Jamila, the dressmaker protagonist of the "3+1 Wives" series, so their mom advised them to turn to her if they really needed better quality lingerie for their magnificent breasts.
When they entered her home, they found her nursing her children Yussuf and Yahya, sided by her husband Zayan and her co-wive (and lesbian lover) Sharifa, by now pregnant with a couple of non-conjoined identical twins.
Dionaea and Cytherea noticed that they weren't just helping Jamila -- they were leering at her as if they were waiting for their turn to use her body, and her breasts. Their arousal was so apparent that even Dionaea and Cytherea caught it, all the more so as they had a lesbian relationship.