Feature models are used for variability management in software product lines. Instead of developing a single feature model, merging small models can be an effective solution to obtain a unified view. Since each stakeholder views the product family from a different perspective, conflicts may occur during merging. In this research, merging of feature models arising from different viewpoints is considered. A normative procedure is proposed to merge feature models by applying local rules. This procedure can merge feature models with cross-tree relationships between sibling features. Application of the local rules is demonstrated with examples.