Is a child who dies of heart disease before puberty considered a martyr and will he intercede for his parents?

Muslim children who die before puberty are in Paradise under the care of Abraham (peace be upon him), but they are not considered martyrs, even if they died from a painful illness. They do not attain the virtues of battlefield martyrs who were killed in the path of Allah, such as interceding for seventy of their relatives, as this is exclusive to the battlefield martyr.