While my husband was traveling on business out of state, under time pressure he pushed my naive 24 year old son to take a legal document requiring my signature (without my prior knowledge or consent) to give him permission to execute construction flip loan documents on our company's behalf. My son only takes orders and does not direct anything. His father does all company directing. My son per his dad's instructions brought these papers to my husband's sister's house to have her forge my signature because his dad had said that it was "no big deal" and an "insignificant" 1 page document. I found out about it and was able to get my son to email me a copy of the forged document (a really poorly done forgery nothing like my signature). My son also sent an email (likely scripted by his dad) explaining why they had "no time" to get ahold of me for my actual signature or permission. Yet they had taken the time to get another family member's signature to trace and got her permission. So I also have that email stating that they didn't ask me first. My husband's sister did the actual forgery I'm told, but what are the legal ramification of the forgery for my husband who directed it to be done and my son who also knew about it and saw it? I believe my husband knew I had reservations about this flip loan and wanted to bypass getting my permission.
The contract based on the fraud is voidable and all three are criminals
Your husband and sister are guilty of fraud, your son of accessory to fraud. All three are also guilty of a criminal conspiracy to commit fraud. Punishment varies, for example, in new-south-wales fraud has a maximum penalty of 10 years gaol. These are unlikely to be at the maximum end but you never know.
In addition, people convicted of financial crimes like fraud are usually prohibited from being company directors or managing a company at a senior level.
You are also in an invidious position now that you know - if you benefit from the loan you also become an accessory.
If the fraud is proven, the bank cannot rely on this document so the “construction flip loan” (whatever that is) would need to be undone - probably by repayment immediately. The bank could also sue the criminals for their losses - the fees and interest they would reasonably have expected to make on the loan. The bank would probably insist on involving the police.