Your 'father' slips through the hallway, peeking into each room, quickly passing over your sleeping girlfriend and little brother it determines your mother is the biggest threat and must be assimilated. To avoid creaking on the stairs it reforms it's shape into a thick pool of blue liquid, slowly dripping down the stairs and collecting at the base of the steps. Your mother is oblivious to her impeding fate as she lays on her stomach, eyes locked on her reality television. Your mother despite being in her mid-40's is still quite the prize, today she is sporting a tight pair of grey yoga pants that hide nothing of her luscious rump and a loose pink tank top that allows her E-cup breasts to breathe.
The creature stares at your mother, pondering at this new gender and begins to consider how the human biology works. Unlike itself, the person in front of it does not seem to have a penis or testicles, in it's own language it thinks to itself; 'Is this one faulty? has it not developed properly? Or perhaps this species consists of multiple sexes, either way it will become a valued member of the hive.'
"Hey honey, c'mere." The creature says in your dads voice, leaning in next to her. With her eyes closed she giggles and pulls it in for a kiss, unbeknownst her husband is long gone, the creature notices the two large lumps on the woman's chest, further puzzling it in it's assessment of humans. Your mother opens her eyes, pulling back and jumping up at the sight of her jellified husband, quickly the creature grabs your mother, pulling her inside of it's own body and reshapes into a large blob. Your mother's screams are muffled by the thick jelly slowly filling her throat, to assimilate her faster, the creature removes her clothing and inserts it's jelly into her vagina and anus, to her own surprise making her moan in pleasure. As your mother's cells are incorporated into the jelly, her form begins to change, her breasts retracting and ovaries pushing outwards as she becomes a male variant of the hive species. As her mind is taken over her flesh follows suit with hubby, although this time taking on a red color.
Finished with its prey, father releases your mother, the new red jelly man standing up and examining it's body, a sinister smirk dressed across his face. Like your mother it retains her figure, albeit with no breasts and a large penis and testicles. Pleased with its creation it telepathically commands mother to assume the mating position, he bends over, displaying his even more wobbly ass for father as he quickly pounces, thrusting his new cock into your former mother's rectum. The creatures are astounded by the sheer pleasure of human sex, completely unlike anything experienced on the homeworld. Mother clings onto the coffee table to keep himself upright as Father forcefully penetrates deep inside of him, causing the place-mats and mugs to rattle against the glass, this paired with the slapping sound of colliding testicles generates quite a loud noise, and unbeknownst to them, awaking 'their' younger son.