The Office of Personnel Management soon will announce rules to allow employees to take up to 12 weeks per year of paid sick leave to deal with a family emergency or care for a loved one. The proposal will follow a White House announcement made last year that said the government should be a model to the private sector for improving such leave benefits. The rules could be effective as soon as the end of March. Currently, leave is available to federal employees under the Family and Medical Leave Act for such purposes, but that leave is unpaid.