I always learnt/thought bitcoin blockchain is like a linked list and it can have only one parent and one child at max
Inside each block there is an eighty bytes block header with space for exactly one previous block hash of length 32 bytes. So, no, you can not create multiple children/parent in normal scenario.
But, sometimes there is a fork, there there will be multiple next block from a single block. Theoretically there could be unlimited number of such things, but for bitcoin those are bound to be very few and very short lived because of the cost of producing a block and one fork chain will win and everybody forget the other forks/next blocks.