if you dislike someone and (say) your boss ask you to share a cubicle with that person, how do u feel? you will hate that someone more and you hate (say) your boss for ignoring the situation between 2 of you.
another scenerio, if you dislike someone. you and that someone are sit a distance apart. your colleague points out to you once in a while about the someone's kind / weak side. how would you feel? along the way, you will feel that you get to 'know' the person better... and u start empathizing...
first, it's a character and personality difference. it's also mental perception of each other. it would be good if you be the in-between and explain to them (one at a time) the reason why the other react this way and the causes for the reaction. you should focus on letting them know each other better than putting them physically together (now) hoping the situation will become better.
physical closeness is only one of the avenue to make them live w each other. but does not achieve the ultimate objective of acceptance, sharing & caring for each other. that i think is what you wanted ultimately. They may end up burying their unhappiness deep in and away from you.
moreover, they are reaching puberty stage. unless there's a shortage of room in the hse, if not, not advisable for long term.
as on how they can live with others in adulthood, they will find their way. no worries.