Running two companies is never an easy thing, but the good news is that there are several examples of executives who were successful at it. Steve Jobs did it, and Elon Musk is doing it as we speak. With Jack Dorsey recently returning to Twitter (NYSE:TWTR) as permanent CEO, and his other company, payments start-up Square, now filing to go public, Dorsey may soon find himself in charge of two public companies.

There are only so many hours in a day, and even though Square and Twitter are literally headquartered next door to each other in downtown San Francisco, investors must inevitably acknowledge the risk factor of having a CEO whose time is split. Don't just take my word for it; Square lists this consideration as one of its important risk factors in its recently filed S-1 Registration Statement:

Jack Dorsey, our co-founder, President, and Chief Executive Officer, also serves as Chief Executive Officer of Twitter. This may at times adversely affect his ability to devote time, attention, and effort to Square.

Can Dorsey juggle both companies at once?

A bigger stake
Currently, Dorsey has an estimated net worth of about $2.3 billion, and naturally, the majority of this wealth is attributable to his stakes in Twitter and Square. But he has relatively less invested in Twitter. Here are his current stakes in both companies, according to recent SEC filings.

Company

Shares Owned

% Ownership

Twitter

21.9 million 

3.2%

Square

71.1 million

24.4%

Source: SEC filings. Figures do not include options or unvested shares.

At current prices of just below $31, that Twitter stake is worth approximately $672 million. There isn't a lot of available data on Square's share price in private markets, but the company was valued at $6 billion a year ago, and Dorsey holds a 24% stake in the company. That would suggest that his position in Square is valued at more than $1.5 billion.

Dorsey recently purchased nearly 32,000 shares of Twitter in the open market in August as a very public vote of confidence -- he tweeted to tell the world about it -- but the reality is that he sold roughly 380,000 shares in the year before that.

It's worth pointing out that Dorsey has given away more than 15 million Square shares during the past two years to help underserved communities, and plans to give away even more. While a larger stake in Square doesn't necessarily mean that Dorsey will be more devoted to the payments start-up, he does stand to lose a lot more if Square performs poorly.

Founder's pride
There's also a possibility that Dorsey has more pride as a founder in Square, because he is just one of two founders at the payments start-up. On the other hand, Dorsey was one of Twitter's four founders. But Twitter was Dorsey's first big hit. Dorsey started Square after co-founder Jim McKelvey was unable to accept a credit payment for a piece of art, and the pair decided to do something about it.

There's no way to measure Dorsey's pride in each respective company that he's founded. But both companies require a lot of work. Twitter is in obvious turnaround mode after continued stagnation in user growth. I have my own doubts about Square's upside potential considering its focus on small and local merchants.

Evan Niu, CFA has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Twitter. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.