The phrase "sickly child" refers to a child who often gets sick or has a weak immune system. They may be frequently ill or have ongoing health problems. Full definition
Even in the case of a mass murderer on the order of Joseph Stalin it has become part of his legend that he was emotionally scarred by having been a weak and sickly child with a brutally abusive father. (tamsinshaw.com)
The end result of focusing solely on these «felt needs» of course, is weak and sickly children who never grow up or mature. (redeeminggod.com)
I was prediabetic at age 7 and severely overweight my entire childhood, I was also a very sickly child in and out of the doctors office almost constantly. (drlam.com)