Leo, I cannot see the connection between 'sincere' motives (although maybe misguided), and 'ego' in the sense of arrogance. I really can't. It is possible to pray with bad motives, just as it is possible to give a speech filled with hate-filled poison. I am speaking of prayer in the general sense. Whatever is in your heart, will come out in your actions and speech (and prayers). If it's selfish to want your loved one to recover then good. Selfishness in this sense is part of the survival instinct that propels us to act in ways to survive. Prayer is just an expression of that hope and need to survive, or get better or resolve an issue. There are arrogant pray-ers, no doubt but I maintain the act of praying is not arrogant or as I can see it egotistical. My way of viewing this is very different to yours.
"The eternal mystery of the world is its comprehensibility"
Albert Einstein
Albert Einstein