How to ask toddler if he wants a sibling?

Time is of the essence right now. How can I get my almost 3 year old son to understand what it means to have a brother or sister to the point that he can tell us if he truly desires having a sibling? Like I said, time is of the essence as I don’t have many more years to be able to give him that. All advice is appreciated.

Add: I know this isn’t his decision, but his input is important. Therefore, I would like advice on how to get a 3 year old toddler to understand the concept of being a big brother.

Another Add: This isn’t an issue of having the means and desire for another child. The issue at hand is timing. My son is only 3(almost) and I am 40, my husband 43. We are happy with it being the 3 of us. But my son is a nurturing boy and does interact with other children naturally well, especially younger than him. I do believe he will desire having a sibling. But as I stated, I am realistic about my capabilities of having another. So, I am curious, from others that have more than one child, how did you go about explaining the concept of being a big brother/sister to your oldest? My husband and I have different childhoods. He had a terrible family life and ended up hating having a sibling. I had my sibling on my Christmas list. But I am 8 years older than my sister. That I can’t do with my son. So, for me, it’s now or not at all. There isn’t a lot of time to wait until my son learns to express it entirely on his own.