We’re in our mid-thirties and have a 2-year-old daughter.
My wife has a very good relationship with her siblings (5 of them), so she feels life without siblings is boring.
I’ve lived far away from home, most of my life, almost independently, struggled through without much help, so don’t feel so strongly about our daughter having a sibling.
Her biggest concern is that once we both are gone, if our daughter remains the only child, she would be all by herself in the world, with no one to share her life, with other than her spouse.
My argument to this – there are millions of kids like that, so what?

This is not a financial related decision, I have a well-paid job and am financially stable. I think I've been a great father to my kid and have done the absolute best for her and will continue to do so.
But I have to admit, parenting has been hard. Takes away a lot of your time and interest in doing other things. Adding another just going to overwhelm me psychologically.

Too add fuel to fire, this topic of another child started when I told my wife I got another job, with a significant increase in pay compared to my current job but we have to relocate to another state (KL to JB).
Initially, before I received the offer, my wife agreed to relocate.
However, after accepting the offer, when I was looking for places to stay online, she dropped the bomb having another child.
She told me, if I don't agree, she and my kid will not relocate and she has given me a week to decide.

I got no issue of relocating on my own (I would do it anyway even she disagreed to relocate the first time) but to emotionally blackmail me using my kid here is unfair.

What are your thoughts about having another child? Have you had a similar experience on this topic? Would like to hear your thoughts and feedback.

Initial I never wanted kids. Obviously, it was our (my) fault for not discussing this before marriage. My wife only started hinting about having kids because all her friends were getting preggy/kids. Crying every night. I gave in.
When she was pregnant, she asked if we can have the kid in Malaysia, and wanted the baby to grow with all the other family members (especially the grandparents)
I felt it was a good point. I left my high paying job abroad and since I was already in a stable financial situation, I decided to return to Malaysia.
Now she is at it again. She started the conversation by saying her friends are adding more family members, her parents for having 5 kids, even some of MY friends who are getting 2nd or 3rd child.
I hate comparisons used as an excuse to win a discussion/argument

Im not going to have children so that they can take care of me in the future, they are not my retirement plan. I will have everything sorted for myself and my wife (retirement and medical).
I will provide the best for my kid. What she does with it and becomes in the future, that's her choice.
We bring them to this world, it's unfair to put the burden on them in the future - regardless of the number of children I will have.