Bronx and state politicians are endorsing legislation Thursday that would tighten penalties for parents convicted of killing their children. Currently, parents found guilty of killing a child can be released after spending 25 years in prison. The new legislation calls for first-degree murder charges for such a crime, which would result in a sentence of life in prison without parole. The proposed law would apply in cases when children under 18 die at the hands of a parent. The legislation comes after 7-year-old Nixzmary Brown was found beaten to death in her Bedford-Stuyvesant apartment. Her stepfather, Cesar Rodriguez, along with the girl?s mother, is charged with second-degree murder and a host of other charges. If convicted, both parents could get out of prison within 25 years, which prosecutors say is not long enough.The bill must go before the state Legislature for approval.