Mere similarity is not a sufficient condition to constitute infringement. Whether there is infringement or not, there are specific basis for determination: comprehensive coverage, equivalent substitution, redundant designation, estoppel, etc. (For specific terms, please check the information or search online). If your new model falls within the protection scope of someone else's invention, but is novel, creative, and practical compared with other inventions, your new model is someone else's subsidiary invention. Within the authority period, each person has a veto power over this new patent. That is, anyone who wants to implement the above-mentioned new plan must obtain the permission of both of you at the same time. Even if you two want to implement the plan, it is no exception. Only if he allows you can you implement it; if you allow him, can he implement it. This is cross-licensing. I suggest you study the information on patent regulations. I believe it will be helpful to you. The online bookstore is very convenient and comprehensive. Highly recommended [Patent Examination Guide 2010] is about one hundred yuan.