You asked

Should siblings (even twins) share a room?

How well your children adapt to sharing a room will depend on a lot of factors, including their individual personalities and temperaments and on their ages. For instance, a toddler who shares a room with an infant probably won’t grasp that your baby needs quiet to sleep while an older child would.
Then there are practicalities. Vastly different schedules, special needs, or even preferring to sleep with a nightlight (while the other sibling doesn’t) can cause problems when children share a room. Some children, on the other hand, particularly twins or siblings of similar ages, tend to do better when they share a room. They have a built in companion and playmate, and some children even sleep better when they share a room.
Even so, while this arrangement might work while your children are younger, as they get older, that may change, as their need for privacy increases. Let your children, their behaviour, and their needs be your guide but by all means, if it seems feasible, give room sharing a try. You might find that your children love it.

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