Company Owning Majority Shares of Another Company

In analyzing the value of a company, should the shares that they own in another company be included in the value (market cap) of the company?

For example, if publicly traded company A with a market cap of 1 billion owns 50% of the shares of publicly traded company B with a market cap of 500 million, does this mean that 250 million of company A's market cap comes from their holdings of company B?

I am looking into two companies where one company is the majority shareholder in the other and was wondering if I bought the larger one if that would effectively be investing in the smaller one too.