Brothers battle it out for their senile dad?s inheritance while they encounter unforeseen changes in their DNA due to an alien entity.

I like the idea of combining sf and brother's battle. This is what is interesting for me and in my opinion you should keep it. BUT you have to build a strong link between the two concepts so that it will become One concept. The heritance and the sf element could be combined.

for exemple:

"When two brothers found a mysterious sphere at their senile father's house, they start battle over the inheritance while experiencing strange mutations in their bodies and minds".

I don't see the point of the alien DNA technology as a plot gimmick. Or the need.

If the purpose is to introduce a factor into the story that alienates two brothers who were previously simpatico, living in harmony, you don't need to tweak their DNA. Fighting over an substantial inheritance left intestate can divide and alienate family members who had been living in peace and harmony for decades. This I know from personal experience!

Also, by introducing the alien DNA tweaking, you seem to have rendered the characters as plot puppets of the alien; the alien is pulling their strings via their DNA. They appear to be victims who are not in charge of their own destiny. The conflict does not arise from their own character flaws. It arises from an external, an alien factor, over which they have no control.

The latest draft of the logline is more succinct but presented no clarifying changes and lacks an inciting incident better to specify it than infer it: After their father dies two brothers?

Why are there two protagonists? Obviously they are both equally deserving of the inheritance so if you pin them up against each other they both come across as inappropriate when trying to get more than the other.

Why would the audience root for both whilst being not nice and inappropriate? More so in a dual protagonist plot both characters need to take the same action to achieve the same goal only with two separate inner journeys. Here you have two protagonists taking the same action to achieve two contradicting goals what will result in ongoing shifting dramatic points of view throughout the film. This will dilute the experience and likely weaken the plot around each character.

Perhaps specify a single protagonist and have him try to do the right thing but have the other brother be the antagonist. Then you have a clear driving goal to drive the plot with a MC the audience wants to see on his journey.

Lastly I still don't see the connection to alien technology, extra terrestrial life or off planet DNA infections how ever you word it these are all external to the plot. They present complications that don't contribute to the stakes, obstacles or antagonistic forces and introduce genre confusion.

Don't confuse curiosity for confusion.

Having two unrelated separate subject matters with two separate plot elements that don't set each other up will be confusing.

However if you use one to setup the other and demonstrate a clear and direct connection but hide the details you will get curiosity this logline does;t achieve that.

How about this:
Brothers battle it out over their senile dad?s life and inheritance as their DNA enhances the good and evil within them after they find a sphere from outer space.

Brothers battle it out over their senile dad?s life and inheritance as their DNA enhances the good and evil within them after they find a sphere from outer space.