triggers

can any one please help me out of this scenaio

1. There are two objects ParentObject__c and ChildObject__c which don't have master-detail relationship. ChildObject__c has lookup relationship with ParentObject__c. You have a requirement like - Whenever a ParentObject__c record get inserted, create two ChildObject__c records. You also need to replicate the roll-up summary field functionality on ParentObject__c. Means whenever a ChildObject__c record gets inserted, updated or deleted; evaluate the no. of child records for a parent and populate it on ParentObject__c. The field to populated count is NumberOfChilds__c on ParentObject__c.