Well with DS I managed (he loves books and was an easy toddler, so no need) without TV till he was nearly 2. DD was born when he was 21 months and soon after Cbeebies became invaluable! I don't whether it was because he didn't have TV when he was younger, but at 3.5yrs now he loves TV and would watch it all day if I let him, so I have to restrict it to an hour a day max.
DD has grown up around the TV being on when DS is watching his programmes. So has had small doses of it, she is 22 months now. She doesn't care much for it at all, will watch for a minute or two and then wander off to play. Will watch Peppa Pig though. On the otherhand, DS is transfixed when the TV is on, will not do anything else.
But (not sure this is anything to do with TV viewing, but I think it could be), DS was a very early talker, who spoke in sentences before 2, great vocabulary and clear speech. DD is way behind him in terms of speech at her age.