"besides since" is not a correct phrase in written English.
You could use other phrases, such as "in addition to" or "aside from," in place of "besides since" in your writing. For example, "I had no other options besides to buy a new laptop, since my old one broke down."
And besides, since when was cost a consideration in a midlife crisis?
And besides, since it's the current "Mr. Cool of Hollywood" Iron Man himself, so how bad could it be?
Besides, since the swatted mosquito will most likely die instantly, "it's not going to suffer".
"Besides, since 9/11, most of the people here have had to adjust to new security measures in their own states and cities".
Besides, since tax havens exist to protect property rights to the fullest extent possible, the impact on more fundamental rights is disastrous.
Besides, since I've always seen West Islip as a fishpond of banality, maybe it's apt that Mr. Lazio has become its poster boy.
Besides, since the laws are widely ignored in practice, the labour market is more flexible than it seems.The fiscal-responsibility bill would seem to have the best chances.
Besides, since his lying was so sincerely done, why should anyone believe his most sincere apology?The presentation of Mr Starr's report to Congress now raises the stakes.
Besides, since the December summit in Copenhagen, China has hinted it might go its own way on climate change.Popular Japanese attitudes towards China suffer from the same doublethink.
Besides, since this is a manufacturer shortage not a stock problem, going online doesn't help (actually, that's not quite true – Argos still has a small number of the ones with the Mohicans.
Besides, since most people -- whether they admit it or not -- like to blame their folks for how they turned out, there's cathartic release in watching the vivisection of those who eat their young for breakfast.
