Q: When I pray a petition, I can’t help feeling that if I pray for one person only, the prayer will be stronger or more effective than if I pray for 20 people at once. For example, is “Please help David” a stronger prayer than “Please help all my family”?
A: Prayer is certainly powerful, but I’m not sure that we should spend time and energy on figuring out the relative power of different ways of praying. What’s more important than the number of people prayed for is the purity of intention on the part of the individual praying and that person’s willingness to connect honest prayer to generous action.
You seem to fear that praying for several people at the same time will dilute the effect of your prayer. I think that may be imposing human categories onto God. You probably want to avoid that because it suggests that prayer is a human object rather than a response to God’s grace.