One, two, three or ten children. It is a personal choice, we should not even be discussing it.
'Children have no one to relate to and are somewhat introverts' – is that your observation or have you got this from the children?
I agree with Umesh, I think it is better to have one child and raise that child to be a fine human being rather than struggling with raising children and getting perturbed by their stubbornness and behavioural issues.
I have seen people reach out for advice on social forums seeking solutions for correcting their adult child's erratic behaviour because they had pampered and spoilt their child, when young. You too must have come across them.
Parents have a responsibility towards their child, and if they can provide positive reinforcement, and give their single child their time and attention then it's a job well done.
I have one child and she has turned out pretty good, by all standards. She is confident, intelligent, loving and caring and knows what she wants in life, and is willing to work towards her goals. I do not think that her being an only child dented her prospects or her personality in any way. I think she is definitely more poised than those who grew up with siblings. The proof of the pudding is in the eating!
"A love affair with knowledge will never end in heartbreak." -Michael Garrett Marino